The protein, Akt-1, is a signaling protein that is produced in increased amounts by several kinds of human cancer cells. This protein is believed, among other things, to be involved in a complex process that transmits a survival signal to cells under stress, which may allow preferential survival of tumor cells by helping them avoid the normal progression to apoptosis, or cellular death. This protein is also involved in the transmission of control signals related to important physiological functions, such as insulin metabolism and protein synthesis, as well as various aspects of cell growth and differentiation, including the growth of platelets, skin cells, and fibroblasts. Alteration of the Akt-1 protein can have a pleiotropic effect. That is, mutation of the protein can result in multiple, apparently unrelated, effects within an animal's cells. These effects point to the importance of Akt-1, and its potential usefulness in the treatment of disease, provided the appropriate precision in use can be obtained. Thus, the objective here is to inhibit the production of Akt-1 in the right context, that is, when it sends an undesirable survival signal to cancer cells.
Akt-1 exerts its effect through a process known generally as cell signaling. Cell signaling is a mechanism, or biological pathway, that regulates cell growth and survival. Various chemicals produced by the body, such as growth factors and cytokines, function as extracellular signals that interact with a cell's membrane. The membrane propagates the signals to the inside the cell, where various biological effects are manifested. A signal pathway is activated when an external signaling molecule, or ligand, binds to the cell membrane, and a protein kinase or a phosphatase modifies a target protein at a specific location on the molecule. Protein kinases are enzymes that (along with other materials such as phosphatases) regulate the propagation of the extracellular signals to inside of the cell. Protein kinases function to phosphorylate proteins at specific locations, namely at serine, threonine, and tyrosine residues. As a result, kinases are classified by their specific phosphorylation site. Akt-1 (also, “PKB alpha and RAC-PK alpha”) is a member of the AKT/PKB family of serine/threonine kinases. In many signaling pathways, several steps using different kinases may be involved. An “upstream” kinase can phosphorylate, or activate, a “downstream target” protein, which may in turn be a kinase that has several targets. Cell signal propagation pathways are often found to be altered in cancer and other disease conditions. Such changes may indicate that this signaling pathway is affected when cells lose their normal signaling mechanism.
For example, tyrosine kinase activity, or signaling, becomes overactive in the early stages of cancer development, or oncogenesis. One consequence of this increased activity is an increased activity by another kinase, PI 3 kinase. PI 3 kinase is known to activate a number of members of the AKT/PKB family, and elevated levels of AKT/PKB have been observed in breast and other cancers. In a recent study, the function of Akt was the only factor found to be affected by an altered tumor suppressor gene, PTEN, in fruit flies. (Stocker, et al., Science, 2002, 295: 2088).
Due to its pleiotropic effect on, that is, its importance to, many metabolic pathways in the cell, Akt-1 has been extensively studied as a drug target for cancer and diabetes. Inhibitors of upstream kinases for Akt-1 have been the major focus on developing drugs that might change Akt-1 function. However, this approach was not yet proved specific enough, because the inhibitors were toxic to cells generally.
Other strategies aimed at inhibiting Akt-1 function have involved the use of various inhibitors for the upstream kinases immediately responsible for phosphorylating Akt-1. However, these strategies are not specific to Akt-1, and other important proteins were altered as well.
Another approach has been proposed, namely to use antisense oligonucleotides, to modify small portions of the gene that controls the expression, or production of, Akt-1.
U.S. Pat. No. 5,958,773 issued to Monia, et al., Sep. 28, 1999, relates to the use of various antisense oligonucleotides for the modulation of expression of nucleic acids encoding Akt-1. Results are reported in terms of inhibition of production of Akt-1. The specific oligonucleotides disclosed and claimed in the present invention were not disclosed in that patent.